Seals are sealing elements of silicon or similar material, which are generally used for sealing connector housings or, for example, electrical apparatuses. To effect such sealing, a stripped wire is first fitted with a seal and then crimped with a metal contact. The contact is embodied in such manner that it holds the seal tightly on the wire.
Seal-fitting devices may be fully automatic or semiautomatic. Fully automatic seal-fitting devices are used, for example, in wire-processing machines that automatically present the stripped wire to, and remove it from, the seal-fitting apparatus. Semiautomatic seal-fitting devices are typically used as bench top devices, wherein the wire must be inserted into a holding gripper of the seal-fitting apparatus by hand.
In the case of seal-fitting devices that operate on simple fitting principles, the wire is pushed directly into the seal. This carries the risk of the internal contour of the seal being damaged. Moreover, this operation cannot be performed with already stripped wires, since the strands of the wire would then be bent. Although stripping after seal-fitting would be possible, it would result in productivity losses and further disadvantages.
In more advanced seal-fitting devices, before the seal is fitted it is expanded by being pushed onto an expansion collar, which is embodied as a hollow cylinder. When the wire is being fitted, it is pushed into this expansion collar, and then the expansion collar is pulled out between the wire and the seal, which is held by a releaser. A seal-fitting device in which the seals are expanded before being pushed onto a wire is known, for example, from EP-B1-0 410 416.
Known from document US 2008/155816 A1 is a technical solution that allows a flexible seal to be pushed onto a wire. A seal-transfer device and a seal-holding device are used. A seal from a stock is fed into the seal-holding device. Fastened onto the seal-transfer device is a hollow cylindrical body, which is pushed into the seal. Hereinafter, this body is referred to as “hollow cylinder”. Before being pushed in, the seal is moved by the seal-holding device into a transfer position. A pressure-body is then deployed to exert counter pressure against the seal from one side while the hollow cylinder is pushed into the seal. During the pushing-in as described, a needle-shaped guide element sits inside the hollow cylinder in such manner that an end of the needle that tapers to a point projects from an opening of the hollow cylinder, the opening facing in the direction of the seal. The hollow cylinder, along with the needle sitting inside it, is pushed into the seal, while the pressure-body exerts counter pressure as stated. As a result of the needle tapering to a point, the joint pushing-in of the hollow cylinder and the needle proceeds gently. After the hollow cylinder has been pushed into the seal, the needle is retracted to create room inside the hollow cylinder to push-in a wire-end. After the wire-end has been pushed in, the hollow cylinder is retracted, and hence the seal is transferred from the hollow cylinder onto the wire.
The following describes characteristic features, as well as advantages and disadvantages, of the two most common fitting principles. A more easily maintainable and more rapidly operating seal-fitting device is disclosed in EP-B1-0 626 738. EP-B1-0 626 738 discloses a seal-fitting device in which a seal, on being removed individually from a feeder-rail, is mounted onto an arbor and, on the arbor, is pushed from a smaller to a larger diameter so as to expand the seal. After the arbor has been swiveled into the correct position, an expansion collar, which is embodied bipartitely, and a releaser, which is also embodied bipartitely, embrace the seal. By means of a relative movement of the releaser, the seal is pushed onto the expansion collar. The fitting operation per se is performed by the expansion collar, along with the seal and the releaser, moving over the wire. During the operation, the releaser remains stationary until the expansion collar has completed its movement, which causes the seal to be released onto the wire.
It is an advantage of this approach that the seal is expanded in gently progressive manner. Moreover, the seal cannot slip off the expansion collar, since the former is held by the releaser. Disadvantageous is that through the bipartite embodiment of the expansion collar, the latter has a relatively large external diameter, since the wall thickness cannot be reduced limitlessly.
EP-B1-1 022 821 discloses a further apparatus for seal-fitting. After the seal has been individually picked, it is mounted on a tubular monopartite expansion collar. While the seal is being swiveled into the horizontal fitting position, it is not additionally held. After the seal is embraced by a bipartite releaser, fitting takes place through movement over the wire, followed by retraction of the expansion collar.
This approach has the advantage that the monopartite expansion collar can be embodied very thin-walled, as a result of which the seal need be only slightly widened. Disadvantageous is that, with certain types of seal, it is difficult to push the seal onto the expansion collar without the seal subsequently slipping off again. The great elasticity of the seal hinders the pushing-on operation.
Both fitting principles have the disadvantage that, when the seal is being pushed onto the expansion collar and being released, the seal is not supported on the same shoulder, and hence is pressed together in two opposite directions. This can cause folding-back of the seal, and in series production generally results in a greater variation of the position of the seal.